This section provides background information related to the present disclosure which is not necessarily prior art. This section also provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
The primary function of a valve stem seal in an internal combustion engine, for example, is to allow adequate lubrication at the valve stem/valve guide interface while minimizing internal oil consumption. A valve stem seal assembly generally includes a rigid shell structure and a seal body, with the assembly having a generally hollow interior adapted to receive a valve stem guide. Typically, the shell structure supports the seal body, which surrounds the valve stem in order to essentially “meter” the provision of oil for lubricating the valve guide's inner diameter and the outer diameter of the valve stem. At the same time, however, the valve stem seal serves to minimize the amount of oil that can be drawn into the combustion chamber or pass to the engine's exhaust.
The rigid shell structure typically includes a can or cylindrical member and a spring seat that is press fit thereon and extends radially outwardly to provide a surface for the valve spring. The interface between the can and the spring seat is generally rigid and not flexible. This rigid interface results in stress concentrations that can cause cracking or breaking of the spring seat during vehicle operations due to resonance conditions caused by valvetrain harmonics. In particular, a valve spring sits on the spring seat and applies a force thereon at two locations that are about 180 degrees apart. During certain operating conditions, the valve spring may rotate relative to the spring seat such that the two points of impact between the valve spring and the spring seat rotate along the surface of the spring seat. During resonance conditions, the force of the spring on the spring seat can exceed the design specifications such that fatigue and cracking of the spring seat can occur, resulting in failure of the valve stem seal. While it may be possible to design the valve stem seal to a degree that can accommodate the forces associated with a resonance condition, such valve stem seal would have a significantly greater cost. Thus, it would be advantageous to provide an economical valve stem seal that can accommodate the high resonance loads while reducing the possibility of failure of the valve stem seal.
Additionally, the two-piece valve stem seals typically require manufacture to high tolerances to provide the desired interactions and level of rigidity. The high tolerance requirement increases the costs of the valve stem seal. Thus, it would be advantageous to provide a two-piece valve stem seal with a lower dimensional tolerance such that a more economical valve stem seal may be realized. Additionally, the reduced tolerance requirement may facilitate easier assembly of the two-piece valve stem seal.
A valve stem seal according to the present teachings utilizes a multi-piece construction to reduce the required manufacturing tolerances and/or improve the stress handling capabilities. The valve stem seal can include a first member or can which is assembled to a second member or spring seat. The can and/or spring seat can have a plurality of axially extending resilient fingers that are biased such that when assembled the fingers are bent against the bias due to the engagement between the can and/or the spring seat. The fingers on the spring seat allow the spring seat to bend or move relative to the can to accommodate the loading of a valve spring on the spring seat. The relative movement reduces and/or minimizes the possibility of stress concentrations occurring on the spring seat such that the lifespan of the valve stem seal may be increased. The use of resilient fingers on the can and/or the spring seat reduces the manufacturing tolerances required for the valve stem seal such that a more economical valve stem seal may be realized.
A valve stem seal according to the present teachings can be used in a valve-containing device having a valve with a valve stem thereon. The valve stem seal can include a first member having axially opposite first and second ends with a side wall extending axially therebetween. The first member can have a hollow interior defined at least partially by the side wall. A second member has a radially extending flange portion with an opening therethrough and an axially extending portion circumscribing at least a portion of the opening. A resilient seal body is supported by the first member adjacent the first end. The seal body has a seal body opening therethrough for receiving the valve stem in sealing contact therewith when the valve stem seal is assembled into the valve-containing device. The first member and the second member are assembled together with the second member opening extending around the second end of the first member and the axially extending portion engaged with the side wall. At least one of the side wall adjacent the second end of the first member and the axially extending portion of the second member include a plurality of axially extending resilient fingers with gaps therebetween and that bend radially relative to the respective side wall of the first member and the flange portion of the second member.
A valve stem seal according to the principles of the present invention can be used in a valve-contained device having a valve with a valve stem thereon. The valve stem seal can include a can having axially opposite first and second ends with a side wall extending axially therebetween. The can may have a hollow interior defined at least partially by the side wall. A spring seat has a radially extending flange portion with axially opposite first and second surfaces and a central opening extending therethrough. The spring seat has a plurality of resilient spring seat fingers spaced apart around the opening and extending axially away from the first surface. The spring seat fingers are biased radially inwardly. A resilient seal body is supported by the can adjacent the first end. The seal body has a seal body opening extending therethrough for receiving the valve stem in sealing contact therewith when the valve stem seal is assembled into the valve-containing device. The spring seat and the can are assembled together with the spring seat surrounding the second end of the can. The can extends at least partially through the opening. The spring seat fingers are bent radially outwardly due to engagement with the side wall such that the spring seat fingers apply a radially inward force on the side wall. The spring seat fingers allow the spring seat to move relative to the can when the first surface is cyclically loaded by a valve spring.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.